Is that when using the two in conjunction could produce an effect greater than each considered separately?
Pretty much. This has been proven in rat-studies quite well in relation to nicotine/ETOH. However, human studies mostly indicate that tolerance to this effect is normally quickly achieved, negating this response (at least, the ones I've read do).
As for using two drugs (or more) to balance yourself out, I have to say that this is an area I don't have a great knowledge in. I have read one study that focused on nicotine/alcohol and indicated such through observations of learning performance during drug use, but as I say, it's not really my area of expertise. It's certainly not something I have any personal experience in. Actually, I recall drinking too much coffee once and then trying to balance it out with some cider so I could sleep. Just made me feel doubly wretched.
Teetotal is definitely my personal stasis of choice, although I do rather enjoy the high of having just cleaned a tricky root section (probably because it's such a rare occasion).